Dimmer for LED flashlight

From ScienceZero

A simple PWM dimmer for a single cell lithium-ion LED flashlight

This simple circuit makes it possible to adjust the brightness of a high power LED flashlight without wasting energy in large resistors. A voltage doubler is used to make sure the MOSFET gate is fully turned on even when the battery is dropping in voltage.

None of the component values are very critical.

C1 should be selected to give a PWM frequency of about 2 kHz

C2 should be significantly larger than the gate capacitance of the MOSFET

RV2 must be adjusted so that the MOSFET turns fully on at 2.85 V battery voltage

The 4093 may be replaced by a 74HC14, other CMOS inverters may work but will be more prone to instabilities.